1. Field of the Invention
The present invention relates to a semiconductor device including a capacitance type sensor such as an Si (silicon) microphone.
2. Description of Related Art
An Si microphone manufactured by MEMS (Micro Electro Mechanical Systems), increasingly applied to a portable telephone in place of an ECM (Electret Condenser Microphone), is widely noticed nowadays.
In order to integrate the Si microphone and an integrated circuit such as a signal processing circuit into one chip, proposed is formation of the Si microphone by a technique (CMOS processing technique) of forming a CMOS (Complementary Metal Oxide Semiconductor) device.
The Si microphone formed by the CMOS processing technique has a structure obtained by arranging a diaphragm on the surface of a silicon substrate having a recess formed at the center thereof to be opposed to the recess and opposing a back plate to the diaphragm at a small interval, for example. The silicon substrate is so provided with the recess (cavity) that the diaphragm vibrates when a sound pressure (sound wave) is input in the Si microphone. When the diaphragm vibrates while a voltage is applied between the diaphragm and the back plate, the capacitance of a capacitor formed by the diaphragm and the back plate changes, and voltage fluctuation between the diaphragm and the back plate resulting from this change of the capacitance is output as a sound output signal.
In the steps of manufacturing the conventional Si microphone, however, the recess is formed by deeply digging down the surface of the silicon substrate, and hence long-time etching is inevitably required, to disadvantageously increase the time for manufacturing the Si microphone.